Known in the art has been a hybrid vehicle provided with an internal combustion engine and motor able to output power for driving use, and a battery storing power generated by output of the internal combustion engine and supplying power to the motor (for example, PTLs 1 and 2). In such a hybrid vehicle, the driving mode is switched between an EV mode in which operation of the internal combustion engine is stopped and output of only the motor is used as the power for driving use, and the engine operating mode in which output of the internal combustion engine is used as the power for driving use.
In the vehicle control system described in PTL 1, the driving mode is selected based on the relative magnitude of the first fuel consumption rate of the internal combustion engine when outputting power for driving use and the second fuel consumption rate of the internal combustion engine when storing power in the battery. By doing this, the driving mode with the optimum fuel efficiency becomes selected more often and the fuel efficiency of the internal combustion engine is improved.
Further, in such control, even when the driving output demanded by the driver is small such as at the time of driving at a low speed, the engine operating mode is frequently selected by a change in the accelerator operation etc. For this reason, forced charging of the battery due to a drop in the remaining battery power can be kept from occurring, and the fuel efficiency of the internal combustion engine can be kept from deteriorating due to forced charging.